Centrifugal fan

ABSTRACT

A centrifugal fan includes a centrifugal impeller rotatable around an axis of rotation; a drive motor of the centrifugal impeller; a casing including a central portion for housing the motor and the centrifugal impeller and a tangential outlet channel in communication with the central portion. The casing has an inlet opening in the central portion and an outlet opening in the tangential outlet channel. The fan includes a system for cooling the motor including the impeller, a ventilation channel operating between the tangential outlet channel and the central portion for generating a flow of cooling air, a collar integral with the centrifugal impeller extending axially from the centrifugal impeller around the motor and a plurality of blades of the motor for generating a tangential cooling component which combines with the flow of cooling air and generating as a resultant, a helical vortex around the motor.

TECHNICAL FIELD

This invention relates to a centrifugal fan and in particular acentrifugal fan comprising a system of cooling the motor of the fan.

BACKGROUND ART

In the automotive field (for coach, truck and similar applications) theuse of centrifugal fans driven by DC motors of the open type iswidespread.

These fans are conveniently provided with systems for cooling therelative drive motors based on a forced circulation of cooling air.

FIG. 1 illustrates a prior art centrifugal fan, in a schematic viewpartly in cross-section.

This type of fan comprises a scroll-shaped outer casing 100, formed by acentral portion 101 and an outlet channel 102 in communication with thecentral portion 101.

The casing 100 has an inlet opening 103 formed in the central portion101 and an outlet opening 104 formed at the end of the channel 102.

A motor 105, generally of the “open” type and equipped with aerationholes 105 a, is mounted inside the scroll for driving a centrifugalimpeller 106, rotating around its axis R, which sucks air at the inletopening 103 and introduces the blown air into the channel 102 of thescroll 2.

After being placed in rotation, the impeller 106 generates a pressuredifference between the inlet opening 103 and the outlet opening 104 soas to generate a flow F of air along the channel 102. Generically, it isindicated that there is a high pressure at the outlet, or outside, ofthe fan whilst there is a negative pressure (compared with the outlet)at the inlet, or inside.

The cooling system of the motor 105 comprises a recirculation duct 107having inlet in communication with the channel 102 and outlet incommunication with the central portion 101. The duct 107 collectspressurised air at the outlet of the casing 100 so as to form a flow RFof cooling air which is pushed, from the over-pressure coming from theimpeller 106, to the central portion 101 at the rear part of the motor105. In this way, the flow RF of cooling air passes through the aerationholes 105 a of the motor 105 removing the heat directly from thewindings of the motor 105 and again reaching the inside of the impeller106 and from there reintroduced into the channel 102.

The reference markets for these fans require more advanced solutionsfrom a point of view of the electronic drive of the motor, which must beintegrated in the motor whether it is of the brushless type or the DCtype, and at the same time from a point of view of the lifetime andreliability of the motor under harsh operational conditions.

The main obstacle to the adoption of these solutions is due to therelatively poor performance of the cooling systems of the prior artmotor which cannot guarantee the optimum operational conditions of thefans operated.

Consider, for example, that in the case of drive electronics integratedin the motor the limit operating temperature must be up to 50° C. lessthan the temperature of the windings and a cooling system of the motoris therefore essential which can remove large quantities of heat inorder not to exceed the limit operational conditions.

It should be noted that both the lifetime of the product and thepossibility of operating under harsh operational conditions are closelylinked to the possibility of guaranteeing an adequate and efficientcooling of the motor and the relative electronics.

DISCLOSURE OF THE INVENTION

In this context, the main technical purpose of this invention is toprovide a centrifugal fan which is free of the above-mentioneddrawbacks.

One aim of this invention is to provide a centrifugal fan equipped witha highly efficient cooling system.

Another aim of this invention is to provide a fan equipped with acooling system which is able to remove large quantities of heat from themotor driving the impeller, also, for example, in the case of adoptionof a closed motor in which the cooling components may not be directlyexposed to a forced flow of cooling air.

The technical purpose indicated and the aims specified are substantiallyachieved by a centrifugal fan according to independent claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention are more apparent inthe non-limiting description which follows of a preferred embodiment ofa centrifugal fan as illustrated in the accompanying drawings, in which:

FIG. 1 illustrates a schematic view of a prior art centrifugal fan.

FIG. 2 illustrates a cross-sectional schematic view of a firstembodiment of a centrifugal fan according to this invention;

FIG. 3 illustrates a top plan view of a second embodiment of acentrifugal fan according to this invention;

FIG. 4 illustrates a schematic cross-section according to the line IV-IVof the fan of FIG. 3;

FIG. 5 illustrates a conveniently scaled-up portion of the fan of FIG.4;

FIG. 6 illustrates a top plan view of the fan of FIG. 3, with some partscut away to better illustrate others;

FIG. 7 illustrates a first perspective view of a first embodiment of aimpeller of a centrifugal fan according to this invention;

FIG. 8 illustrates a second perspective view of the impeller of FIG. 7;

FIG. 9 illustrates a partly schematic cross-section of a portion of athird embodiment of a fan according to this invention;

FIG. 10 illustrates schematic perspective view of a detail of thecentrifugal impeller of the fan of FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

With reference to the accompanying drawings, with particular referenceto the FIG. 2, the numeral 1 denotes a centrifugal fan according to thisinvention.

The fan 1, which has an axis of rotation R, comprises a casing, orvolute or scroll 2, an electric motor 3, preferably of the closed or“sealed” type, having a corresponding shaft 3 a, located inside thecasing 2 and supported by it and a centrifugal impeller 4, illustratedin particular in FIGS. 7 and 8, driven by the motor 3.

The impeller 4, rotatable around the axis R, comprises a plurality ofcentrifugal blades 5, having main extension according to the axis R, anda first and a second support ring 6, 7 between which the blades 5extend.

The impeller 4 has a first inlet 8, formed by the opening delimited bythe support ring 7, coaxial to the axis R, and a tangential outlet 9defined, in practice, by the spaces between the blades 5.

The impeller 4 comprises a hub 10, connected to the first support ring6, for coupling with the motor 3.

The hub 10 has a sleeve 11, for coupling with the shaft 3 a, from whicha plurality of arms 12 extend for connecting with the ring 6.

The hub 10 also comprises a central portion 13 which extends from thesleeve 11 between the arms 12 and delimits, with the arms 12 and thesupport ring 6, a plurality of openings 14.

As illustrated, for example, in FIGS. 2, 3 and 4, the motor 3 ispartially inserted inside the hub 10 whilst in alternative embodimentsnot illustrated the motor 3 is outside the hub 10.

The aforesaid casing 2 has an axial inlet opening 15, that is, coaxialwith the axis of rotation R (and therefore coaxial with the inlet 8 ofthe impeller 4), and a tangential outlet opening 16, located in a knownmanner with respect to the impeller 4, for circulating the air moved bythe impeller 4.

The casing 2 comprises a main body which has a central portion 17 inwhich is formed the inlet opening 15 and an outlet channel 18, whichextends tangentially from the central portion 17 and is in fluidcommunication with it, and at the free end of which is located theoutlet opening 16.

The fan 1 comprises a cover 19 for closing the casing 2 to which,preferably, the motor 3 is anchored.

In practice, the cover 19 is located, relative to the motor 3, from theopposite part of the impeller 4 and it is coupled to the central portion17 of the main body.

The cover 19 forms a housing 20 for the motor 3 in which the motor 3 ispartially located.

More specifically, the cover 19 has an inner cylindrical side wall 21and an inner rear wall 22 joined with the side wall 21 delimiting thehousing 20 and the motor 3 is located in a coaxial fashion inside thehousing 20.

More specifically, with reference to the FIG. 5, the upper portion 3 bof the motor 3 is the portion of the motor 3 which is housed in thehousing 20 and the lower portion 3 c of the motor 3 is the portionpartly inserted in the hub 10.

An air circulation zone 32 is defined between the motor 3, specificallybetween its upper portion 3 b, and the cover 19.

The fan 1 comprises a cooling system for removing heat from the motor 3by means of a flow RF of cooling air directed from the inside of thecasing 2 towards the outside of it.

According to this invention, as will be clarified below, the flow RF ofcooling air consists of a tangential component and an axial component,directed according to the axis of rotation R.

The tangential component and the axial component are added vectoriallygenerating, as the resultant, a helical vortex RF around the motor 3.

With reference to FIG. 2, in a first embodiment, the cooling system ofthe motor 3 comprises, for generating the aforesaid axial component, theimpeller 4 and a duct 30 having inlet 26 in the outlet channel 18 andoutlet 27 in the central portion 17, substantially at the motor 3.

In use, an over-pressure is created at the outlet 9 of the impeller 4,in particular also at the inlet 26 of the duct 30.

This over-pressure pushes air along the duct 30 from the inlet 26towards the outlet 27; the flow of air exiting from the duct 30 formsthe aforesaid axial component.

For generating, in use, the aforesaid tangential component of thecooling flow RF, the cooling system comprises a collar 28 integral withthe impeller 4 and extending axially from the impeller 4 towards themotor 3, outside of it, and a plurality of radial blades 29, supportedby the collar 28 and facing the motor 3.

The collar 28 is made in a single body with the impeller 4 and extendsfrom the support ring 6 on the opposite side with respect to the blades5.

The radial blades 29 extend between the support ring 6 and the outercollar 28 and they extend from the latter towards the motor 3.

The outer collar 28 together with the blades 29 surround the motor 3 andin particular the upper portion 3 b of the motor.

The aforesaid housing 20 is designed to accommodate, in addition to themotor 3, also the collar 28 and therefore the blades 29.

The blading constituted by the blades 29, together with the outer collar28, placed in rotation with the impeller 4, being a single body with theimpeller, generates a contribution to the cooling flow RE which formsthe aforesaid tangential component.

The effect of the rotation of the blades 29 is, in other words, that ofdragging the air contained in the hollow space between the blades 29 andthe motor 3, generating the tangential component of the cooling flow RF.

The aforesaid axial component is advantageously directed from the upperportion 3 b of the motor towards the lower portion 3 c of the motor,inside the casing 2, in such a way that the cooling flow RF, resultantfrom the combination between the tangential component and the axialcomponent moves, through the openings 14 of the hub 10, to the inside ofthe impeller 4, from where it is expelled outside the casing 2 throughthe outlet opening 16.

In a second embodiment, illustrated in FIGS. 4 and 5, the cooling systemcomprises a hollow space 31, or annular channel 31, formed between thecylindrical outer wall of the collar 28 and the cylindrical side wall 21of the housing 20.

The annular channel 31 places the channel 18 in fluid communication withthe central portion 17 of the casing 2 at the upper part 3 b of themotor 3.

More specifically, the cover 19 is shaped in such a way that the annularhollow space 31 is in fluid communication with the channel 18.

With reference in particular to FIG. 5, reference numeral 31 a indicatesthe inlet of the annular channel 31 and reference numeral 31 b indicatesthe outlet of the channel 31.

The cooling system comprises, similarly to the first embodiment, thecollar 28 integral with the impeller 4 and extending axially from theimpeller 4 towards the motor 3, outside of it, and the radial blades 29supported by the collar 28 and facing the motor 3.

The collar 28 is made in a single body with the impeller 4 and extendsfrom the support ring 6 on the opposite side with respect to the blades5.

The radial blades 29 extend between the support ring 6 and the outercollar 28 and they extend from the latter towards the motor 3.

The outer collar 28 together with the blades 29 surround the motor 3 andin particular the upper portion 3 b of the motor.

The aforesaid housing 20 is designed to accommodate, in addition to themotor 3, also the collar 28 and therefore the blades 29.

The blading constituted by the blades 29, together with the outer collar28, placed in rotation with the impeller 4, being a single body with theimpeller, generates the contribution to the cooling flow RF which formsthe aforesaid tangential component.

The effect of the rotation of the blades 29 is, in other words, that ofdragging the air contained in the hollow space between the blades 29 andthe motor 3, generating the tangential component of the cooling flow RF.

In use, the impeller 4 pushes air at high speed along the canal 8.

The high speed air generates a Venturi effect which generates, in turn,a negative pressure at the outlet 31 b of the channel 31.

The negative pressure causes a suction effect along the hollow space 31of the flow of cooling air.

In other words, a suction flow is generated in the annular channel 31directed from the inlet 31 a to the outlet 31 b.

In practice, the suction along the hollow space 31 generates, inside thecentral portion 17 of the casing 2, the so-called axial componentsubstantially directed according to the axis of rotation R of the motor3 inside the casing 2.

This axial component is sucked inside the impeller 4 through the inlet8.

The axial component is advantageously directed from the lower portion 3c of the motor towards the upper portion 3 b of the motor, inside thecasing 2, in such a way that the helical cooling flow RF, resultant fromthe combination between the tangential component and the axial componentmoves, through the openings 14 of the hub 10, through the impeller 4, tothe zone 32 from where it is expelled outside the casing 2 through thehollow space 31 and the channel 18.

The axial component combines with the tangential flow due to the blades29 generating the aforesaid helical vortex RF which is carried frominside the casing 2 to the outside of the casing 2 through the hollowspace 31 and the channel 18.

In the preferred embodiment illustrated, the annular channel 31 has theoutlet 31 b delimited between the cover 19 and the impeller 4, havingdimension “h” of the same order of magnitude as the dimension “h1” ofthe channel 31 between the collar 28 and the cylindrical side wall 21delimiting the housing 20.

In other words, the cover 19 is shaped in such a way as to delimit theoutlet 31 b with the first support ring 6 and/or with the blades 5.

In the embodiment illustrated, the outlet 31 b of the annular channel 31is advantageously formed by the support ring 6 and specifically by anannular rim 60 of it which faces a corresponding annular portion 19 a ofthe cover 19.

The annular hollow space 31 is in communication with the air circulationzone 32, where the inlet 31 a is formed.

In this way, in use, the flow drawn along the hollow space 31 combinesin the zone 32 with the tangential flow due to the blades 29, generatingthe aforesaid vortex RF around the motor 3 which is sucked into thechannel 18.

In the aforesaid air circulation zone 32 the flow of cooling air RFtouches the cover of the motor 3 removing heat from it.

The air circulation zone 32 is defined between the rear wall 22 of thehousing 20 and the rear surface 33 of the motor 3 to which it faces.

In practice, the inside of the housing 20 is provided with the space forthe circulation of the air both between the side wall and between thebase wall of the motor 3 and the cover 19.

A third embodiment of a fan according to this invention is illustratedin FIG. 9.

In this solution, compared with the second embodiment, the suction ofthe cooling flow across the hollow space 31 is assisted by a series ofcentrifugal blades 40 positioned on the outside of the collar 28 forforcing the air from the hollow space 31 towards the outlet opening ofthe channel 18.

The centrifugal blades 40 extend from the opposite side with respect tothe motor 3 and form a second auxiliary centrifugal fan 41 which furtherpushes the cooling flow, resultant from the combination of thetangential component with the axial component, from the hollow space 31towards the outside of the casing 2.

The blades 40 are advantageously made in a single body with the collar28 and extend outside the collar, as also shown in FIG. 10.

In the preferred embodiment illustrated by way of example, each blade 40is formed as an extension of a corresponding blade 5 of the impeller 4,as shown in FIG. 10.

Preferably, the cooling system, and the blades 29 in particular, aredesigned in such a way that the tangential component is of an order ofmagnitude greater than the axial component for effectively removing heatfrom the motor 3.

The duct 30 external to the casing 2 in the first embodiment and thehollow space or annular channel 31 in the second and in the thirdembodiment define a ventilation channel forming part of the coolingsystem of the fan 1 thanks to which the cooling flow RF defined as ahelical vortex removes heat from the motor 3.

The motor 3 is therefore touched by high speed air on the external skinwhich is particularly effective in the removal of heat.

The effect of the rotation of the blades 29 is in other words, that ofdragging the air contained in the hollow space between the blades 29 andthe motor 3, generating the aforesaid tangential component.

The motor is enveloped by a helical vortex which is very effective forforced cooling without using an axial component that is detrimental forthe efficiency and the noise level of the fan.

The axial component is necessary for transporting the quantity of heatcollected by the aforesaid vortex RF outside the “motor zone”.

The centrifugal fan provided with the cooling system as described allowsthe adoption of closed or sealed motors, which work well in harshambient conditions, also with drive electronics integrated inside.

The cooling system as described allows the lifetime of the fan to beextended by up to more than 30,000 working hours compared with prior artfans.

The proposed solutions allow maximisation of the cooling of the motordriving the impeller, minimisation of the sources of fluid dynamic noiseand, at the same time, minimisation of the costs for equal performancelevels by avoiding adoption of the connecting duct between fan outletand housing of the motor.

The adoption of the annular suction channel inside the casing of the fan(axial component) allows both the noise of the air due to the fluiddynamics and the vibrations to be reduced compared with prior artsolutions,

1. A centrifugal fan comprising a centrifugal impeller rotatable aroundan axis of rotation; a drive motor of the centrifugal impeller; a casingcomprising a central portion for housing the motor and the centrifugalimpeller and a tangential outlet channel in communication with thecentral portion, the casing having an inlet opening in the centralportion and an outlet opening in the tangential outlet channel, a systemfor cooling the motor comprising the impeller and a ventilation channeloperating between the tangential outlet channel and the central portionfor generating a flow of cooling air, the fan characterised in that thecooling system comprises a collar integral with the centrifugal impellerextending axially from the centrifugal impeller around the motor and aplurality of radial blades supported by the collar and facing the motorfor generating a tangential cooling component which combines with theflow of cooling air generating as a resultant a helical vortex RF aroundthe motor.
 2. The fan according to claim 1, wherein the casing comprisesa cover closing the central portion positioned coaxially to the motor onthe opposite side with respect to the centrifugal impeller, theventilation channel being at least partly formed between the outersurface of the collar and the cover.
 3. The fan according to claim 2,wherein the ventilation channel has an annular outlet, delimited betweenthe cover and the centrifugal impeller, having dimension of the sameorder of magnitude as the dimension of the ventilation channel betweenthe collar and the cover.
 4. The fan according to claim 1, wherein thecooling system comprises a plurality of centrifugal blades extendingfrom the opposite side of the motor with respect to the collar, forforcing the cooling flow along the tangential outlet channel.
 5. The fanaccording to claim 4, wherein the centrifugal blades extend from thecollar and form a single body with the collar.
 6. The fan according toclaim 1, wherein the collar and the first radial blades are made in asingle body with the centrifugal impeller.
 7. The fan according to claim1, wherein the motor is at least partly inserted in the centrifugalimpeller.
 8. The fan according to claim 1, wherein the casing comprisesa cover closing the central portion positioned coaxially to the motor onthe opposite side with respect to the centrifugal impeller, the coverhaving a cylindrical inner side wall and an inner rear wall delimiting ahousing in which the motor is inserted, the ventilation channel beingformed between the collar and the cylindrical inner side wall, an aircirculation zone being formed between the inner rear wall and a rearsurface of the motor, the ventilation channel and the circulation zonebeing in fluid communication with each other.
 9. The fan according toclaim 1, wherein the ventilation channel is formed by a recirculationduct outside the casing having inlet in the tangential outlet channeland outlet in the central portion.